Bladder Outlet Obstruction

What is Bladder Outlet Obstruction?

Bladder Outlet Obstruction (BOO) normally occurs in Singapore when there is a blockage beyond the neck of the bladder, where it connects to the urethra. Such a blockage may take the form of bladder stones, a tumour (either cancerous or benign), an enlarged gland, or even scar tissue. Commonly associated with prostate problems, BOO is more common in men than women and tends to affect those above the age of 65.

What are the common causes Bladder Outlet Obstruction in Singapore?

BOO can have a number of causes, including:

  • Bladder Stones
  • Tumours
  • Urethral scar tissue
  • Previous urinary surgeries
  • Cystocele
  • Pelvic Organ Prolapse
  • Urethral, vaginal, or cervical cancer
  • Benign Prostate Hyperplasia
  • Prostate Cancer
  • Presence of other disorders such as Parkinson’s disease or multiple sclerosis
  • Functional voiding issues

What are the symptoms of Bladder Outlet Obstruction?

Some common symptoms to look out for when it comes to BOO are:

  • Urinary hesitancy
  • Incomplete voiding
  • Nocturia
  • Urinary frequency
  • Pelvic/abdominal pain
  • Painful urination

When should I visit the doctor?

You should visit a doctor if you are experiencing any of the above symptoms, especially if you experience pain when you urinate. You should also see a urologist if you are showing any signs of infection, such as a fever, or if you have noticed any changes in the smell or appearance of your urine. 

Your doctor will be able to begin treatment and provide advice on what lifestyle changes you can make to alleviate your symptoms.

What can I expect during my first consultation?

Your consultation will generally begin with a series of questions that aim to help your doctor understand your medical history and symptoms. A physical examination and various diagnostic tests may be carried out such as blood tests or a uroflowmetry. It is highly likely that your urologist will order diagnostic imaging tests, such as an ultrasound or a CT scan.

How is Bladder Outlet Obstruction diagnosed in Singapore?

There are a number of diagnostic tests that can be useful in cases of BOO. These include:

  • Blood tests
    Some common examples of blood tests used in cases of BOO are renal panels to check kidney function or prostate-specific antigen (PSA) tests, which look for elevated PSA levels.
  • Urinalysis and Urine Culture
    Your urine sample will be sent to a laboratory to check for any blood or infection in your urine.
  • Ultrasound Kidneys, Bladder and Prostate
    An ultrasound can show any potential issues with the structure of the bladder, prostate or kidneys, and in particular, will be able to detect any obstructions present.
  • Flexible Cystoscopy
    This is a relatively painless test that uses a fibre-optic telescope to inspect the bladder, urethra. In males, the prostate gland will also be examined.
  • Uroflowmetry and Residual UrineThis test measures your voiding function by analysing the speed and volume of your urination. Following the test, your urologist will perform a bedside ultrasound bladder to check for the presence of any residual urine.

Can Bladder Outlet Obstruction be cured?

BOO can generally be cured by treating the cause of the condition. For example, bladder stones can be removed surgically or benign prostate hyperplasia treated with medication. In more complicated cases where the underlying cause of BOO cannot be cured or will require long-term treatment, the symptoms of BOO can still be managed using medication or management techniques such as intermittent catheterisation.

How is Bladder Outlet Obstruction treated in Singapore?

Treatment for BOO will depend on the underlying cause of the condition.

Bladder stones

BOO can be caused by bladder stones. Usually, surgical treatment is required. 

In more serious cases, a transurethral cystolitholapaxy may be necessary. This procedure involves the use of a laser to break the stone into smaller pieces, which are eventually flushed out from the bladder. The stones can also be surgically removed through an open surgery if they are too large or too hard to be broken up. If there is concomitant enlarged prostate, a prostate surgery (transurethral resection of prostate) may also be needed. If a neurological voiding issue is the primary reason for the bladder stone, other management options may be necessary.

Growths, tumours or urethral scar tissue 

BOO caused by growths, tumours, or urethral scar tissue can be treated by surgically removing these obstructions, while BOO caused by cancer or other diseases can be treated by addressing these conditions.

Benign Prostatic Hyperplasia (BPH) 

BOO caused by benign prostatic hyperplasia can sometimes be treated with oral medications such as alpha-blockers or 5-alpha reductase inhibitors. In more serious cases of benign prostate hyperplasia, surgical intervention may be necessary. The most common procedure used to treat this condition is called a transurethral resection of the prostate, where part of the prostate is surgically removed. Minimally invasive methods have been developed recently for BPH as well.


In women, BOO can also be caused by a cystocele, where the walls of the bladder have weakened and dropped into the vagina. In these cases, the BOO can be treated using a pessary, which fits inside the vagina to hold the bladder in place. Surgery may be required for serious cases.

For management of BOO symptoms, various medications may be prescribed, or you may be asked to perform intermittent self-catheterisation if there is incomplete voiding. Your doctor will instruct you on how to insert a catheter into your urethra at regular intervals in order to empty your bladder completely.


BOO is generally an uncomplicated condition that can be easily treated by addressing the cause of the bladder outlet obstruction. This condition should be treated early as it can cause more serious complications when left untreated. 


Residual urine may lead to recurrent UTIs and any backflow of urine into the ureter and kidneys may eventually result in kidney failure. If you suspect that you may have BOO, please see a urologist as soon as possible. Once they have determined the cause of your condition, an appropriate treatment plan can be devised and put into motion.

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Dr. Fiona Wu 2

Dr Fiona Wu
Consultant Urologist

MBBS (S'pore), MRCS (Edin), MMED (Surg),
MMED (Clinical Investigation),
FRCS (Urol) (RCPSG), FAMS (Urology)

Dr Fiona Wu is an experienced Consultant Urologist and is the Medical Director of Aare Urocare.

Prior to her private practice, she spent 15 years in public service. She was a Consultant in the Department of Urology at National University Hospital (NUH), Alexandra Hospital and Ng Teng Fong General Hospital.

She believes in treating urinary incontinence in a holistic way using minimally invasive methods – this ranges from laser treatment, neurotoxin injections, electromagnetic nerve stimulation to minimally invasive surgeries, etc. She worked closely with the gynaecology and colorectal departments to treat complex pelvic floor conditions and continues to do so in her own practice.

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